1. Field of the Invention
The invention relates to a punching bag, more particularly to a punching bag which includes an outside bag enclosing two envelopes that are respectively filled with a weighing member and a fluid.
2. Description of the Related Art
A conventional punching bag, as shown in FIG. 1, includes a base unit which has a hollow casing 1 filled with water or sand via an inlet 101 disposed on a top face of the casing 1, a connecting unit 2, and a cylindrical bag 3 filled with gas. The connecting unit 2 includes an upper rod 201 inserted into the bag 3, a lower rod 203 inserted into a through hole 102 in the casing 1, and a spring coil 202 interconnecting vertically the upper and lower rods 201, 203. The base unit provides stability, while the bag 3 can be used for punching.
Another conventional punching bag, as shown in FIG. 2, includes a base 4 having an inner space filled with a liquid 401, a connecting part 5 connected to the base 4, and a punch body 6 connected to the connecting part 5. Both the connecting part 5 and the punch body 6 are inflatable.
In the above-mentioned conventional punching bags, as both the gas-filled bag 3 and the punch body 6 are inflated to a high pressure, the external surfaces thereof are usually tensed and stiff so that a realistic feeling experienced during boxing cannot be obtained. In addition, since the bag 3 and the punch body 6 are limited to gas-impervious materials, it is difficult to conduct surface treatment for improving resiliency or softness of the bag 3 and the punch body 6 although formation of decorative patterns is possible.